Multistep navigation and the combinatorial control of leukocyte chemotaxis.

Foxman EF, Campbell JJ, Butcher EC - J. Cell Biol. (1997)

Bottom Line:
Furthermore, cells can chemotax effectively to a secondary distant agonist after migrating up a primary gradient into a saturating, nonorienting concentration of an initial attractant.Together, these observations suggest the potential for cells' step-by-step navigation from one gradient to another in complex chemoattractant fields.We propose a multistep model of chemoattractant-directed migration, which requires that leukocytes display multiple chemoattractant receptors for successful homing and provides for combinatorial determination of microenvironmental localization.

ABSTRACTCells migrating within tissues may encounter multiple chemoattractant signals in complex spatial and temporal patterns. To understand leukocyte navigation in such settings, we have explored the migratory behavior of neutrophils in model scenarios where they are presented with two chemoattractant sources in various configurations. We show that, over a wide range of conditions, neutrophils can migrate "down" a local chemoattractant gradient in response to a distant gradient of a different chemoattractant. Furthermore, cells can chemotax effectively to a secondary distant agonist after migrating up a primary gradient into a saturating, nonorienting concentration of an initial attractant. Together, these observations suggest the potential for cells' step-by-step navigation from one gradient to another in complex chemoattractant fields. The importance of such sequential navigation is confirmed here in a model system in which neutrophil homing to a defined domain (a) requires serial responses to agonists presented in a defined spatial array, and (b) is a function of both the agonist combination and the sequence in which gradients are encountered. We propose a multistep model of chemoattractant-directed migration, which requires that leukocytes display multiple chemoattractant receptors for successful homing and provides for combinatorial determination of microenvironmental localization.

Figure 2: Gradients formed by IL-8 and LTB4 and calculated agonist concentrations for 1 pmol added in well 1. Each curve shows a representative of at least three determinations of the IL-8 (a) or LTB4 (b) concentration gradients in agarose, 30–120 min after addition of radioactive agonist, using the protocol outlined in the Materials and Methods section. Replicate IL-8 gradient measurements were very consistent in shape and magnitude, whereas LTB4 gradient measurements were more variable, especially in magnitude. The concentrations indicated were calculated for a gradient generated by 1 pmol of agonist. (c) Two replicate determinations of the LTB4 gradient at 120 min.

Mentions:
To determine where the edge of the chemoattractant well was during sectioning, we stained the edges of several wells with India ink, cut strips starting at these wells, and prepared them for frozen sectioning as above. The first 60-μm section that lacked visible India ink was taken to represent the first 60 μm of agarose for the gradient plots in Fig. 2.

Figure 2: Gradients formed by IL-8 and LTB4 and calculated agonist concentrations for 1 pmol added in well 1. Each curve shows a representative of at least three determinations of the IL-8 (a) or LTB4 (b) concentration gradients in agarose, 30–120 min after addition of radioactive agonist, using the protocol outlined in the Materials and Methods section. Replicate IL-8 gradient measurements were very consistent in shape and magnitude, whereas LTB4 gradient measurements were more variable, especially in magnitude. The concentrations indicated were calculated for a gradient generated by 1 pmol of agonist. (c) Two replicate determinations of the LTB4 gradient at 120 min.

Mentions:
To determine where the edge of the chemoattractant well was during sectioning, we stained the edges of several wells with India ink, cut strips starting at these wells, and prepared them for frozen sectioning as above. The first 60-μm section that lacked visible India ink was taken to represent the first 60 μm of agarose for the gradient plots in Fig. 2.

Bottom Line:
Furthermore, cells can chemotax effectively to a secondary distant agonist after migrating up a primary gradient into a saturating, nonorienting concentration of an initial attractant.Together, these observations suggest the potential for cells' step-by-step navigation from one gradient to another in complex chemoattractant fields.We propose a multistep model of chemoattractant-directed migration, which requires that leukocytes display multiple chemoattractant receptors for successful homing and provides for combinatorial determination of microenvironmental localization.

ABSTRACTCells migrating within tissues may encounter multiple chemoattractant signals in complex spatial and temporal patterns. To understand leukocyte navigation in such settings, we have explored the migratory behavior of neutrophils in model scenarios where they are presented with two chemoattractant sources in various configurations. We show that, over a wide range of conditions, neutrophils can migrate "down" a local chemoattractant gradient in response to a distant gradient of a different chemoattractant. Furthermore, cells can chemotax effectively to a secondary distant agonist after migrating up a primary gradient into a saturating, nonorienting concentration of an initial attractant. Together, these observations suggest the potential for cells' step-by-step navigation from one gradient to another in complex chemoattractant fields. The importance of such sequential navigation is confirmed here in a model system in which neutrophil homing to a defined domain (a) requires serial responses to agonists presented in a defined spatial array, and (b) is a function of both the agonist combination and the sequence in which gradients are encountered. We propose a multistep model of chemoattractant-directed migration, which requires that leukocytes display multiple chemoattractant receptors for successful homing and provides for combinatorial determination of microenvironmental localization.